There may be no law for emergency via satellite, because it is very new. However in an emergency you always have to help first and later you may ask for compensation. For example if someone has a wound and may bleed out, you may have to take your own shirt to stop the bleeding. Later you can demand compensation for the ruined shirt.
It may depend on if it would technically be possible to use that services spontaneously or if any preparations would be needed, that are only done when you pay for the service.
Just imagine a car having more air bags than the mandatory ones in front of the drivers seats. Wouldn't it be quite a scandal if the additional air bags would only engage if the owner has an extra subscription to use them? Imagine an accident happens and those extra air bags will not engage because the person did not have that subscription and as a consequence that person dies. That is basically what Apple is planning. They should really include the service in the price of their very expensive smartphones.
It would be okay if their were two models. One that has the hardware for satellite emergency and one that does not. If the hardware is not included, it can't work of course. If the hardware is included and just refuses to save a life, because the owner had not paid, that is very problematic at least. It would be like the included air bag that does not engage.